F. Itoh

XPS study of the valence band spectrum of amorphous Fe-B alloys

Abstract XPS spectra of Fe 3 s and Fe 3 p levels and Fe 3 d valence band of amorphous iron-boron alloys were measured as a function of boron concentration over the range from 12 to 25 at% B. It was found that a characteristic hump appeared at lower energy region in Fe 3 d band spectrum of every amorphous Fe-B alloy. The origin of the hump was discussed in terms of the formation of a new bonding state between Fe and B atoms in amorphous Fe-B alloys.

Preparation of AlXTa1−X amorphous alloy powder by mechanical alloying

AlXTa1−X amorphous alloys were produced in the range of 0.10<X<0.90 by mechanical alloying of pure elemental powders of Al and Ta in Ar gas atmosphere at ambient temperature. The crystallization temperature increases monotonically with increasing Ta content to reach to an extraordinarily high value of 1194 K for Al10 Ta90 amorphous alloy.

An X-ray spectrometer for Compton scattering experiments with synchrotron radiation

An X-ray spectrometer has been designed and constructed for Compton-scattering experiments using 29.5 keV X-rays from a vertical wiggler inserted in the 2.5 GeV storage ring of the Photon Factory at Tsukuba. It consists of a bent-crystal monochromator, a Cauchois-type bent-crystal analyzer and a position-sensitive detector. The measured incident flux on a sample is just over 1011 photons/s. An overall resolution in momentum of 0.10 atomic units (FWHM) has been achieved. The Compton profile of an aluminum single crystal was measured with a mean count rate of 28 cps. As a result of the high resolution in the measurements a sharp cutoff at the Fermi momentum was readily observed.

EXAFS study on mechanical deformation for PdSi amorphous alloy

Abstract Extended X-ray absorption fine structure (EXAFS) spectra were measured in situ under several tensile strains to study the atomic-scale process of mechanical deformation in Pd83Si17 amorphous alloy using synchrotron radiation at KEK. With an increase in the tensile strain, the Pdue5f8Si distance shifts to higher R space with little change in the coordination number while Pdue5f8Pd distance is displaced towards lower R space values with a large reduction in the coordination number. During the unloading process, the values of the Pdue5f8Si and Pdue5f8Pd distances do not return to their initial values. From these facts, the deformation mechanism is discussed in terms of the atomic-scale structure.

Challenge to precise magnetic Compton‐profile measurements (invited)

Recent developments of the insertion devices have made it possible to utilize intense hard x rays for precise Compton‐profile measurements. A Compton profile of Si (110), which is measured using 29.5‐keV synchrotron‐radiation x rays, is shown as an example of a precise measurement having a momentum resolution of 0.084 a.u., the best resolution ever achieved. A promising plan is presented on magnetic electron Compton‐profile measurements using circularly polarized 60‐keV x rays from a newly developed multipole wiggler in the 6‐GeV accumulation ring at KEK as an elliptically polarized source.

COMPOSITIONAL VARIATIONS IN THE SHORT-RANGE STRUCTURE OF Ni 1-x B x (x = 0.18 − 0.40) ALLOY GLASSES

The local environments around a B atom in Ni-B alloy glasses containing 18 to 40 at.% B(natural) were observed as a function of B content by total neutron scattering using a spallation pulsed neutron source. B atoms in the alloy glasses prefer to sit in interstices in the trigonal prism consisting of 6 Ni atoms around the whole B content.

High‐resolution Compton profile spectrometer for 29.5‐keV x rays with a combination of crystal analyzer and imaging plate

A high‐resolution Compton spectrometer has been installed for 29.5‐keV incident x rays from a vertical wiggler inserted in the 2.5‐GeV storage ring of the Photon Factory at Tsukuba. This spectrometer consists of bent‐crystal monochromator, a Cauchois‐type bent‐crystal analyzer, and an imaging plate as a position sensitive detector. The overall momentum resolution is 0.084 a.u. for the incident x‐ray energy of 29.5 keV. High‐resolution Compton profile measurements on Al, a quasicrystal Al‐Li‐Cu, and solid and liquid phase of Li are shown to demonstrate the performance of this spectrometer.

EXAFS study on solid state amorphization process of NiNb alloy by mechanical alloying

Abstract The main purpose of this work is to investigate the micromechanism of the solid state amorphization of metals by mechanical alloying. The changes of radial distribution functions around the atomic species of a Niue5f8Nb mixture powder through ball milling were studied by means of EXAFS. The atomic structural change during crystalline to amorphous phase was discussed.

A comparison between Compton scattering and positron annihilation in Ni-B alloy glasses

Abstract Both Compton scattering and positron annihilation measurements have been carried out for four kinds of Ni-B alloy glasses. From the comparison between these two methods, it is concluded that positrons in Ni-B alloy glasses are trapped at vacancy-like sites in the amorphous structure.

Compton profiles of liquid and solid lithium metals

Abstract Compton profile measurements have been performed on liquid and solid lithium metal using 59.54 keV γ-ray from 241 Am source. A difference between Compton profiles in both states has been found.